Same issue here, again it might be complexity. I have quite a large base and game lags most when I am zoomed out. Also when I would try to deconstruct or cancel an order, it would experience lag just as bad. I checked on my Activity Monitor, but none of the resources were even close to being maxed, and I just got the game yesterday. (Jan.8)
-Tamashi
OSX High Sierra
Model Name: iMac
Model Identifier: iMac11,1
Processor Name: Intel Core i7
Processor Speed: 2.8 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 8 MB
Memory: 20 GB